Paper is produced from wood and other plant fibers. The fibers have the property of adhering to each other when overlaid in water and then dried. When wet, they separate from each other again and return to fibers. This characteristic makes paper an ideal material for recycling. However, fibers do degrade after repeated use. Fresh fibers have many folds that make them easy to entwine and hence, the paper strength is greater. Old fibers are less rough because of abrasion and hard to entwine. To keep producing paper, virgin pulp and recovered paper fibers need to be mixed in a ratio best suited to the intended use.